A conventional mounting apparatus for electronic components of the above-referenced type will be described with reference to the drawings. FIG. 3 is a perspective view schematically showing an essential portion of a generally used mounting apparatus for electronic components. In the drawing, reference numerals respectively indicate: 1 a controller, 2 an operation panel, 3 a component feed cassette, 4 a board, 5 a nozzle, 6 a head part having the nozzle 5, 7 an XY robot, 8 an electronic component, 9 an XY table, and 19 a head part-supporting part for moving the head part 6 up and down and also moving in XY directions with the use of the XY robot 7. In the constitution of the conventional mounting apparatus, each part of the apparatus operates in a manner as follows. Specifically, the head part 6 having the nozzle 5 at the head part-supporting part 19 which is positioned by the XY robot 7 sucks the to-be-mounted electronic component 8 by the nozzle 5 from the component feed cassette 3, moves in the XY directions thereby carrying the component 8 sucked by the nozzle 5 to a mounting position, and lowers and mounts the component to a predetermined position of the board 4 securely held at the XY table 9. At the time of lowering the electronic component 8, a descent distance is set to a value obtained by subtracting a thickness of the electronic component 8 from a reference descent stroke and adding a push-in amount of a constant value to the resulting value. After a preliminarily set time has passed with the head part 6 completely descending, i.e., at a bottom dead center of the nozzle, the nozzle 5 rises to a regulated height, whereby one mounting cycle is finished. The cycle is repeated thereafter. Data of the aforementioned descent stroke and push-in amount are input from the operation panel 2 and controlled by the controller 1.
The above operation will be more fully described with reference to a flow chart of FIG. 14A. In FIG. 14A, a state at a descent step of the nozzle after the apparatus starts is as illustrated in (1) of FIG. 14B, followed sequentially by a push-in step in FIG. 14B(2) and a nozzle ascent step shown in FIGS. 14B(3) to 14B(4).
In the mounting apparatus of the prior art, since the push-in amount to mount the component is constant (fixed), irregularities in height of the electronic components and irregularities in mounting height of the electronic components because of a rising or swelling solder cannot be coped with. That is, the component might be pressed too much onto the board when the component is mounted on the board, and leap up due to an elasticity of the board when the nozzle rises afterwards, as is clear from FIG. 14B(3). The component 8 would eventually be displaced as shown in FIG. 14B(4), or the like inconvenience of deteriorating accuracy of the component after mounting is brought about.
The present invention is devised to eliminate the above-described issue, and has for its object to provide an apparatus and a method for mounting components which can prevent displacement of the components after mounting and improve productivity.